Do you allow the TPR to discharge into the WH pan?

I recently learned something. According to NACHI plumbing training course…

(I’ll post that quote later.)

Personally, I don’t think it’s up to me to “allow” anything!

Not allowed in CA. . .

Ok, perhaps I worded it poorly. You know what I mean.

OK. Over half of you are wrong.

NACHI’s training on plumbing:

“A relief-valve pipe terminating into a water leak catch pan is not permitted, because the pan is not an indirect waste receptor. Most pans have only a ¾ inch-diameter (19 mm) drain outlet, which is not capable of gravity draining the pressurized discharge of the relief valve at full flow.”

Not so up in Canada…

About the only place you are going to see a WH pan here is at Home Depot.

Required in Chicago Buildings.(I call them drain pans)

Here are the exact codes.(Chicago )

18-29-504.7.1 Discharge.

 The discharge from the relief valve shall be piped separately to an indirect waste receptor located inside the building. The discharge shall be piped full size and installed in a manner that does not cause personal injury or property damage and that is readily observable by the building occupants. The discharge from a relief valve shall not be trapped. The diameter of the discharge piping shall not be less than the diameter of the relief valve outlet. The discharge pipe shall be installed so as to drain by gravity flow and shall terminate atmospherically not more than 6 inches (150 mm) above the floor. The end of the discharge pipe shall not be threaded.

18-29-504.8 Required pan.

 Water heaters or hot water storage tanks installed in locations where leakage of the tanks or connections will cause damage shall be installed in a galvanized steel or other metal pan of equal corrosion resistance having a minimum thickness of 24 gauge, 0.0276 inch (0.70 mm) Any water heater installed in a cabinet below a counter shall be provided with a drain pan.

Although I’m in California with Jeff (see comment #3), I do have one large jurisdiction here that allows it.

Code Section 3303.6.1 does allow for the discharge pipe to terminate inside a receptacle (or spill pan) as long as an air gap is provided between the end of the discharge pipe and the top rim of the spill pan itself without creating a hazard or potential cause of damage.

The problem here is, the risk of personal injury when the TPR valve discharges. This is because the discharge pipe terminates into a spill pan that cannot safely catch the flow of water or steam during discharge.
When you consider that the TPR valve discharges at 150 psi, which is five times greater than the force of your domestic water system, the scalding water can strike the bottom of the shallow pan and spray out in all directions. A deeper receptacle with adequate circuference would be advisable over the shallower, tightly-fitting spill pans commonly observed in the field. Even better would be to the exterior when possible or to an indirect waste receptor when initially constructed.


What code is that? (It’s not the IRC.) Would you please quote it verbatim?

I report it as improper, also if it is "T"ed into the pan drain line or another T&P discharge line.

IRC Commentary (P2801.5) specifically states that “The relief valve discharge is prohibited from terminating into such pan”

TPRs should not discharge into the safe pan. A safe pan or “water leak catch pan” under the hot water tank is not an indirect waste receptor, because it has usually a 3/4 inch outlet. That’s the determining factor. Now…the floor drain next to it is. The size of the pan’s outlet would have to meet the minimum size of a indirect waste drain pipe (1 and 1/4). At full discharge, the pan would not be able to hold and drain the discharged water - defeating its “intended” purpose.

Has anyone actually tugged on the TPR with a shirt sleeve during an inspection? Oh! Instant heart thumper…

Question: Can a sump pump be an indirect waste receptor with a TPR valve discharge directed towards it?

Chuck’s right, the 2006 IRC (not sure of other versions) states:

And the diagram shows:

You guys are goood.

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The gift will be this marketing tool.

I see this all the time, and I call it out.

There is a problem here with understanding the concept, even for plumbers.

The TPR valve is NOT a water drainage device, although many people, including plumbers, think it is. It is a STEAM drainage device. When those things let loose, what comes out is not water, it is live steam. The reason for the pipe is to have the steam discharge spray on the floor or some other place where it will not hit human beings.

If the pipe “drains” into the pan, it will splash up and scald a person. The amount and flow rate of the discharge is also more than the pan can handle.

Hope this helps;

Here we go again.

Please explain to us how 210 deg. water is steam.:shock:

Under pressure. 210 degrees, under pressure, and then it hits normal pressure and flashes to steam.

Hope this helps;